Displays are used in a variety of electronic devices to present information to users. Emissive displays include light emitting elements that emit light when images are presented on the display. In today's displays, such light emitting elements are often in the form of light-emitting diodes (LEDs), such as those used in a backlight of a liquid crystal display (LCD), or those used in organic LED (OLED) displays.
In traditional LCD displays, the backlight is typically driven at a duty cycle of 100%, which means that the LEDs of the LCD backlight are always on during image presentation on the display. Images change, frame-by-frame, on the LCD by supplying electric current to a layer of liquid crystals that respond (e.g., twist or untwist) in accordance with the supplied electric current. 100% duty cycle LCDs are suitable for some display applications, but not for ones where fine motion rendition is desired, such as virtual reality (VR) display applications. This is because when a 100% duty cycle LCD is embedded in a VR headset, the large field of view (FOV) causes a scene to appear blurry (e.g., streaky or smeary) to the user of the VR headset whenever the user moves his/her head back and forth to look around the VR scene.
In traditional OLED displays, light is not emitted from all of the pixels (i.e., all of the OLEDs) at the same time. Rather, a typical driving scheme used in traditional OLED displays is to sequentially illuminate each row of pixels from the top row to the bottom row during a given frame. If this process could be shown to a user in slow motion, the viewing user would see a horizontal band of light traversing the display from top-to-bottom. In this “rolling band” technique, the rows of pixels (i.e., OLEDs) are sequentially loaded with light output data, followed by an immediate, sequential illumination of the rows of pixels. At each row, as soon as the loading process completes, the illumination process is started, which means that the OLEDs are sequentially illuminated at the same rate that the OLEDs are sequentially loaded with light output data. This type of driving scheme also has drawbacks in fine-motion-rendition applications, such as VR. This is because when traditional OLED displays are embedded in a VR headset, the large FOV causes a scene to appear distorted to the user of the VR headset during head motion (e.g., the VR scene may appear to move as if it were made of Jello, where the scene is squished and/or twisted as the user's head moves back and forth). Because these unwanted visual artifacts also present themselves during head motion, traditional OLED displays, like 100% duty cycle LCDs, are undesirable for use in VR applications.
Yet another known driving scheme for displays with individually-addressable LEDs is a “global flashing” scheme where, for a given frame, all of the LEDs of the display are simultaneously illuminated in synchronization following a “rolling band” type of loading process where each row of LEDs is loaded with light output data in sequence. While this “global flashing” technique mitigates much of the above-mentioned visual artifacts in VR applications, it is cost prohibitive to implement a global flashing scheme to drive the display. This is because a high number of costly hardware components are required to simultaneously illuminate all of the LEDs for each frame. Global flashing can also shorten the lifespan of the display hardware (e.g., the LEDs and the componentry utilized to supply power and electric current thereto) due to the high frequency power toggling used in this driving scheme.
Provided herein are technical solutions to improve and enhance these and other systems.